This invention relates generally to a novel device for use in locking a door from the inside. More particularly, this invention concerns a novel door locking device that provides supplemental locking functions that enhance the security furnished by conventional dead bolt locking assemblies that are activated from the inside by rotation of a thumb knob or the like.
Concern and fear over rising crime rates have recently focused increased attention on improving residential security. Of particular concern has been the increased incidence of crimes involving the breaking and entering of residential properties. For many years, various attempts have been made to provide an adequate and dependable means of locking the doors of residences so as to stop or discourage substantially unauthorized entry.
One of the most commonplace locking devices used for both residential and commercial properties is the dead bolt lock wherein a dead bolt held within the door is thrown into a striker place held within the door jamb. The typical dead bolt locking assembly used for residential doors has a key activated mechanism for opening and closing the lock from the outside and a thumb knob or a similar piece for opening and closing the lock from the inside by rotation of the thumb knob. Typically, the key activated mechanism and the thumb knob are integrally attached to the tumblers of the dead bolt mechanism so that any movement of a key to open or close the lock from the outside necessarily causes and requires movement of the thumb knob to the opened or closed position as the case may be.
When used alone, these conventional dead bolt locking mechanisms suffer from a number of disadvantages. Because they are designed for key-activated entry, such dead bolt locking mechanisms are subject to picking from the outside. In addition, anyone with a key cut to fit the dead bolt mechanism, whether a key for the specific lock involved or a master key, will be able to unlock the dead bolt locking mechanism whether or not the persons inside the residence desire the entry of the person having such key.
There have been a number of attempts in the prior art to provide additional locking security in connection with various dead bolt locking mechanisms. One such attempt is that described by White in U.S. Pat. No. 258,883. White discloses a dead bolt lock with its essential parts contained completely on the inside face of the door and door jamb, rather than within the door body and door jamb body. White attempts to provide an additional measure of security through preventing the key lock from being turned by means inserted into the keyhole from the outside. This is accomplished by adding an additional member to the dead bolt lock, which member is inserted into a key placed in the door keyhole from the inside. White's combined bolt and key fastener suffers from a number of distinct disadvantages. First, the secondary locking function depends both on the presence of a key inserted into the keyhole from the inside and on the engagement of that key by a member attached to the dead bolt lock. Further, activation of White's dead bolt lock does not accomplish activation of his secondary locking means but instead requires a second motion to achieve the additional locking function.
Another attempt at providing increased security from a dead bolt lock is that suggested by Lanes in U.S. Pat. No. 1,700,135. Lanes describes a means of simultaneously preventing the unlocking of a dead bolt lock with a thumb knob while providing an auxiliary pivot bolt lock. The use of any of the embodiments of Lanes requires the additional step of rotation of the auxiliary bolting lock to its locked position following activation of the basic dead bolt lock itself. Thus, to the extent that Lanes describes two locking functions, such functions cannot be activated simultaneously by one single motion.
Another type of attempt in the prior art at achieving additional security from dead bolt locks is exemplified by that described in U.S. Pat. No. 3,927,544 to Klein. An unhinged hasp device is disclosed by Klein for preventing the turning of a thumb knob of a dead bolt lock. It is clear, however, that Klein simply provides a slotted bar that can be slipped over a dead bolt thumb knob but which does not provide any auxiliary dead bolt locking function.
The most recent attempt at preventing keyed entry through a door having a conventional thumb knob dead bolt lock is that disclosed by Lupton et al in U.S. Pat. No. 4,185,483. Lupton describes a door locking device comprising a wedge of rubber placed between the door handle stem and the thumb knob of the dead bolt lock. The wedge of Lupton, however, provides no auxiliary dead bolt locking function.